Arrived on site to perform diagnostic. On arrival business manager stated that he system wasn’t working last week. He thought it was the thermostat so he replaced it with a nest thermostat. It still didn’t work after that so he called out a google technician who came and wired the thermostat correctly. System is now working as it should and can not diagnose since there’s no issue. Checked system operations. Checked temperatures and electrical components. Cycled system through heating and cooling to check for proper temperature splits. Systems are working normally. Operational upon departure.